1. Field of the Invention
The present invention pertains to the detonation of pyrotechnical substances by laser-produced light beams conveyed by optical fibers or cables.
It may be recalled that the term "pyrotechnical substances" is taken to mean primary explosives (such as nitrides, fulminates, tetrazene, etc.), secondary explosives (such as PETN, RDX, HNS, etc.) and pyrotechnical compositions such as flash compositions, compositions for light flares, tracers, smoke shells etc. The various elements used form what is called a functional photopyrotechnical chain. This chain generally consists of three elements:
a laser as a source of energy,
an optical fiber or cable to convey the energy,
a primer detonator or pyrotechnical firing device.
2. Description of the Prior Art
As a laser source, a triggered, pulsed laser is preferably used. A laser of this type is described by C. CAREL and A. P. JOSSE (of the Aerospatiale firm) and P. BALDY and J. REFOUVELET (Ateliers de Construction de Tarbes) in "Initiation d'Explosifs par Laser" (Actuating Explosives by Laser), Communication to the Internation Colloquium on Fundamental and Applied Pyrotechnics: Substances and Systems, 5-7 October, 1982, Arcachon, France.
A photopyrotechnical primer detonator is a device loaded with primary or secondary explosives which may be actuated under the effect of an energy beam such as a laser beam and which procures a shock wave sufficient to actuate another pyrotechnical component charged with explosives. Pyrotechnical firing devices are devices containing a pyrotechnical substance capable of catching fire when it receives a supply of heat, for example in the form of a laser beam, the resultant flame being capable of firing another pyrotechnical composition.
The document U.S.A. 4,391,195 describes a system for actuating explosives with a laser source and optical fibers to convey the energy from the laser to pyrotechnical detonating devices. According to this document, the end of the optical fiber opposite the laser is in direct contact with a substance capable of catching fire, and the energy from the resultant flame is used to detonate explosive charges. However, most of the present-day photopyrotechnical detonating devices have a poor level of imperviousness to the exterior. This fact entails two disadvantages. First of all the pyrotechnical detonating substance is badly protected from external influences (such as damp or atmospheres with varying degrees of corrosiveness), and this can adversely affect its operation. Secondly, when the charge is being fired, there is a risk of efficiency losses due to leakages of gas released during detonation as well as a risk of surrounding equipment being polluted.
An aim of the present invention is to remove these drawbacks by proposing a photopyrotechnical detonating device in which the pyrotechnical detonating substance is protected from adverse external conditions before and during operation, and for which the actuating energy source cannot be damaged by any backthrust of gas under pressure (.ltoreq.400 Kbars) during and after the explosion.